Polymeric vinylidene chloride compositions



Patented Dec. 4, 1951 UNITED STATES PATENT OFFICE POLYMERIC VINYLIDENECHLORIDE COMPOSITIONS Eugene D. Serdynsky, James S. Gowing, and Ralph M.Wiley, Midland, and Carl B. Havens. Hope, Mich., assignors to The DowChemical Company, Midland, Mich., a corporation of Delaware No Drawing.Application March 2, 194.1,

Serial No. 79,313

3 Claims. (Cl. 280-401 nates, as well as their plasticized compositions(all being referred to herein as polymeric vinylidene chloridecompositions) have the tendency to accumulate and retain charges ofstatic electricity. In the case of molded and extruded articles madefrom such compositions, this tendency is especially noticeable, and itbecomes objectionable in articles such as films and woven fabrics havinglarge areas. This undesirable property causes oppositely chargedparticles of dust and lint to collect on the polymeric vinylidenechloride articles in which a charge has accumulated. It also 'makesdifiicult the sepa ration of one film or fabric sheet from another,as'friction resulting from attempted separation of such sheets generatesenough of a charge, of opposite polarity in the opposed surfaces, tocause those surfaces to adhere to one another. Even when handlingpowdered forms of polymeric vinylidene chloride compositions, it isobserved that the powder may be highly charged and that it tends tointerfere with such operations as the dry blending of other modifiers,or sifting to separate particles of specific dimensions.

It would be highly desirable, and it is the principal object of thepresent invention, to provide a means for reducing substantially thetendency of vinylidene chloride polymers and articles made from them toaccumulate or to retain charges of static electricity. A related objectis to provide such means whereby the said undesirable tendency issubstantially permanently reduced. A particular object is to providepolymeric vinylidene chloride compositions substantially free fromtendency to acquire or retain static electric charges. Other and relatedobjects may appear hereinafter.

According to the present invention, the tendency of polymeric vinylidenechloride, and of articles made therefrom, to acquire and retain chargesofstatic electricity is reduced to an unobjectionably low level byadding to the polymer composition and uniformly mixing therewith from0.5 to 5 per cent by weight of a compound selected from the classconsisting of the pentaalkyl tripolyphosphates and the hexa-alkyltetrapolyphosphates, wherein the alkyl groups contain from 3 to 8 carbonatoms. Such compounds 2 have the empirical formula R5P30l0 and RsPqOrsIrespectively. Examples are the penta-propyl, penta-n-butyl,penta-n-amyl, penta-hexyl, and penta-octyl, tripolyphosphates and thecorresponding hexa-alkyl esters of tetrapolyphos-' phoric acid, andtheir isomers. when molded. extruded and woven articles of large.surface area per unit weight, including films, filaments and fabrics,are produced from a polymeric vinylidene chloride composition containingfrom 0.5 to 5 per cent of one of the defined alkyl 7, polyphosphates,the product is noticeably and significantly less prone to acquire andretain static charges than are otherwise identical articles made fromthe same basic composition but without the polyphosphate.

- noted. The more rapidly it loses its charge, the

more effective is the anti-static agent in or on the sample. In anothertest, a sample of the polymeric article is fastened about the rim of arotor which turns at a fixed rate in contact with another rotor turningin the opposite direction at the point of contact (i. e., in the samedirection relative to the axis). A strip of paper is drawn continuouslybetween the two rotors, counter to the direction of rotation of the testsample, and in frictional contact therewith. In each rotation of thesample, it rubs momentarily against the paper sheet, tending to build upa charge, and then it is brought into contact with a grounded copperbrush, which tends to carry away the charge, through a millivolt meter.At a fixed rate of rotation, the time is noted which is required tobuild up the charge to some arbitrarily chosen value. The longer thetime required, the more effective is the anti-static agent in or on thesample.

Using the second described test method, the time required to build up apredetermined charge of static electricity was noted in tests made onmolded compositions containing 3 per cent of the polyphosphate and 97per cent'of a commercial plasticized copolymer of about per centvinylidene chloride and 10 per cent vinyl chloride. with those onotherwise identical control samples The values obtained were comparedcontaining none of the polyphosphatef Typical results are given below:

Time re- 'quired to develop standard charge Modifier Similarlyadvantageous properties are contributed to the compositions by the useof the corresponding propyl, amyl, hexyl and octyl esters.

When using the first test method, to determine the time required to losecompletely the static charge acquired in a. fixed period of time, thecompositions containing from 0.5 to per cent of one of the definedpolyphosphates were discharged in from 5 to 25 per cent of the timerequired by the control samples.

Each of the defined polyphosphates contributes .the desired property tothe polymer compositions, giving effective and substantially permanentprotection against static build-up and static retention to articles madefrom the modified compositions. Y

The invention is applicable to compositions .and articles made from thehomopolymer ,of

vinylidene chloride or from any of the copolymers in which vinylidenechloride predominates, whether or not such articles or compositionscontain conventional plasticizers, stabilizers and similar modifiers.The most common and commercially useful copolymers of vinylidenechloride are those which contain vinyl chloride, vinyl acetate,acrylonitrile, ethyl acrylate, methyl methacrylate, or styrene as acopolymerized constituent, but the invention is not limited to thetreatment of these specific copolymers and articles made from them.

We claim:

1. A composition of matter having little tend- 4 ency to acquire andretain a charge of static electricity, the essential ingredients ofwhich are a polymer in which vinylidene chloride predominates and from0.5 to 5 per cent of the weight of such polymer of a, compound selectedfrom the class consisting of the penta-alkyl tripolyphosphates and thehexa-alkyl tetrapolyphosphates wherein the alkyl groups contain from 3to 8 carbon atoms.

2. A composition of matter having little tendency to acquire and retaina charge of static electricity, the essential ingredients of which are apolymer in which vinylidene chloride predominates and from 0.5 to 5 percent of penta-n-butyl tripolyphosphate, based on the weight of suchpolymer.

3. A composition of matter having little tendency to acquire and retaina charge of static electricity, the essential ingredients of which are apolymer in which vinylidene chloride predominates and from 0.5 to 5 percent of hexa-n-butyl tetrapolyphosphate, based on the weight of suchpolymer.

EUGENE D. SERDYNSKY. JAMES S. GOWING. RALPH M. WILEY.

CARL B. HAVENS.

' REFERENCES CITED The following references are of record'in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Hochwalt et al., Ind. and Eng.Chem.,-vol. 34,

1942, DD. 20 to 25.

1. A COMPOSITION OF MATTER HAVING LITTLE TENDENCY TO ACQUIRE AND RETAINA CHARGE OF STATIC ELECTRICITY, THE ESSENTIAL INGREDIENTS OF WHICH ARE APOLYMER IN WHICH VINYLIDENE CHLORIDE PREDOMINATES AND FROM 0.5 TO 5 PERCENT OF THE WEIGHT OF SUCH POLYMER OF A COMPOUND SELECTED FROM THE CLASSCONSISTING OF THE PENTA-ALKYL TRIPOLYPHOSPHATES AND THE HEXA-ALKYLTETRAPOLYPHOSPHATES WHEREIN THE ALKYL GROUPS CONTAIN FROM 3 TO 8 CARBONATOMS.